Germany's SPD leader calls for a 'United States of Europe' by 2025 and says any countries who disagree should follow Britain's example and leave the bloc

'The leader of Germany's main socialist party has called for a United States of Europe by 2025.

Martin Schulz said any countries who disagree should follow Britain's example and leave the bloc.

He made the plea in a speech to 600 of his Social Democrats at a congress to decide whether to start coalition talks with Angela Merkel's party.

He said: 'I want a European constitutional treaty that creates a federal Europe'.

The treaty would then be presented to all member states for ratification, with those that reject it automatically leaving the bloc, he said.

He suggested a target year of 2025, one century after the SPD first spoke of a future 'United States of Europe'.

Schulz said only a more united EU could meet challenges such as combating climate change or managing mass migration, forcing internet giants such as Google and Facebook to respect civil rights or stopping large companies from dodging taxes.'